Abstract: A reduction of the unevenness of a temperature increase at the end of heating work can be achieved without specific equipment, and with securing the shortening of the working time, which is an advantage of a bulk heating. When a region to be heated of an article made of a thin sheet is heated inductively so that the whole region thereof reaches a temperature equal to or more than a target temperature using an inductive portion of a heating inductor, to which a high-frequency current is applied by a power supply device, by stopping or reducing temporarily the power application of the high-frequency current to the heating inductor during the temperature increase, a temperature difference in the region to be heated is reduced so that the unevenness of the temperature increase at the end of the heating work is reduced by the step of reducing the temperature difference.

Abstract: A heat treatment operation can be executed, suppressing a wave-shaped deformation at a non heat-treatment region of an article to be heat treated. To an elongated-shaped article to be heat treated to which a raised portion extending in the longitudinal direction is formed, a hardening region, as a heat-treated region defined to extend in a longitudinal direction at a part of the raised portion, and a non-hardening region, as a non-heat-treated region defined to extend in the longitudinal direction at flange portion, and other parts of the raised portion are arranged side by side in a width direction orthogonal to the longitudinal direction. The flange portion is clamped by a first and a second clamp, arranged in the longitudinal direction, and one first clamp is a tight clamp for holding fixedly the flange portion and a plurality of second clamps are loose clamps for clamping loosely the flange portion, allowing the article to be heat treated to be convex on the side of the heated hardening region.

Abstract: A heat treatment operation can be executed, suppressing a wave-shaped deformation at a non heat-treatment region of an article to be heat treated. To an elongated-shaped article to be heat treated (10) to which a raised portion (11) extending in the longitudinal direction is formed, a hardening region as being a heat-treated region defined to be extended in a longitudinal direction at a part of the raised portion (11) and a non-hardening region as being non heat-treated region defined to be extended in the longitudinal direction at flange portion (13) and other parts of the raised portion (11) are arranged side by side in a width direction orthogonal to the longitudinal direction.

Abstract: A reduction of unevenness of temperature increase at the end of heating work can be achieved without specific equipment, and with securing shortening of working time, which is an advantage of a bulk heating. When a region to be heated of an article made of a thin sheet is heated inductively so that the whole region thereof reaches a temperature equal to or more than a target temperature using an inductive portion of a heating inductor to which a high-frequency current is applied by a power supply device, by providing a period to stop or reduce temporarily the power application of the high-frequency current to the heating inductor during the temperature increase, a temperature difference in the region to be heated is reduced so that the unevenness of the temperature increase at the end of the heating work is reduced by the step of reducing the temperature difference.